The present invention relates generally to fuels derived from processed biomass, and more particularly to fuels that are a colloidal dispersion of processed heat treated charred biomass that can be used as substitutes for, or additives to, fluid bio-oil based fuels, and fluid petrochemical fuels.
It is widely recognized that the majority of energy produced throughout the industrialized world is based on the consumption of petroleum based liquid fuels. Such fuels have a high energy density, are relatively easy to transport and store, and can be used in a wide variety of engines and heaters. However, as is common knowledge, the in-ground stores of petroleum based products are rapidly declining, and experts predict that new discoveries are not occurring frequently enough to offset the rapid drawdown of currently known reserves. In the parlance of today, these resources are considered to be non-renewable. Furthermore, use of these non-renewable resources are believed to produce climate changes and more immediately identified local environmental effects commonly associated with increased fouling of air and water and are generally considered pollution inducing and having a negative effect on the environment.
Various attempts have been made to identify renewable sources of energy that can be used in place of petroleum based fuels. For example, electricity can be generated using such renewable energy sources as wind, solar, geothermal and hydroelectric. While these energy sources are considered “clean” or “green” because they are renewable, relatively non-polluting, and are thought to produce a minimal to no carbon footprint or reduced emission profile on the environment from their use, they each have drawbacks due to location, convertibility, space, and wind and water availability. Essentially, these renewable resources are not always found in sufficient commercially available amounts in the locations where they are needed to enable their substitution for all commercially used non-renewable resources.
Coal is another source of energy that is widely used, but which is neither clean nor renewable. While advancements in technology have made the use of coal cleaner with less residual ash and lower atmospheric emission, coal cannot be used in all applications, particularly where use of liquid fuel is advantageous. Although coal can be processed into a water-based slurry, such a slurry cannot be used where a low water content fuel is needed to avoid emission of certain oxides and/or other pollutants, or where the water will cause damage to the equipment being powered by the combustion of the coal slurry.
Furthermore, coal slurry or fluid dispersions of coal still do not overcome the detrimental environmental effects caused by the combustion of coal for heat or energy generation. The type of coal typically used today, called steam coal, or sub-bituminous coal, is not pure, and includes a mixture of harmful heavy metals such as mercury and lead, toxins or other minerals such as sulfur that, when combusted, tend to adversely affect the combustion equipment and at the same time disperse into the air and water resulting in potentially harmful effects on people and the environment.
In view of the problems of using coal and petroleum derivatives to generate energy, various technologies have evolved to utilize renewable sources of energy from natural plant material through cultivation or natural growth and regeneration of woody based, grass based or cultivated vegetable based plant materials, such as wood chips, agricultural by-products, cultivated crops or harvested naturally growing plants and the like. However, unless these materials are handled in a particular manner which includes their being dried and processed bundled, chipped, pelletized, cubed, or baled or heat treated, such unprocessed natural plant products, commonly called “biomass,” are difficult to use as fuel. The unprocessed biomass is typically either too wet, too cumbersome or costly to handle and transport, too prone to decomposition or rot when in a stockpile, too bulky and difficult to feed into conventional heat or energy generation equipment, or are simply too full of non-combustible, non-natural fiber materials, or contaminants such as metal, plastic, sand, gravel, dirt or other ash causing products to effectively bring them from the field, farm or forest directly to a heat or power generating plant for use.
All solid fuels power plants, including coal and biomass power plants are typically designed, engineered and built to use one type or class of fuel and are not easily reconfigured to change from one fuel type to another. For example, coal fired power plants cannot burn biomass without expensive and major engineering changes in their operation systems, usually rendering them unable to revert to coal once the changes to permit biomass combustion have been made. Biomass power plants using certain types of woody based fiber including wood chips in a specifically designed boiler system cannot be fed into the system alongside curbside garden variety aggregated biomass or crop generated by-products without special handling and pre-processing of the alternative fuels. Furthermore these natural cellulosic materials are comprised of a variety of differing cellular mechanical structures and chemical bonds which create their own sets of problems with respect to reduction of moisture content, management of size reduction or alteration, and particle production and handling to permit suitable commercial feeding as a fuel into conventional biomass heat or energy generating equipment.
The handling of biomass is problematic, and typically requires that a dedicated biomass generation plant be specially engineered to use certain specific types of biomass fuels. As discussed above, the biomass fuel type used in such a generation plant is typically not interchangeable with another type of biomass fuel. Biomass can be aggregated, chipped or chopped, ground up, dried and burned, but not all biomass can be mixed and processed homogenously, dried and burned with the same equipment and in the same manner. In addition, raw, unprocessed biomass type fuels (even if they have undergone a preliminary process, such as chipping or shredding) are not easily convertible or reducible into smaller more manageable and uniformly sized particles due to their inherent diverse ligno-cellulosic chemical and mechanical cellular bonds.
Consumption of biomass for the production of heat is one of the oldest processes known to man, and the production of energy from heat to steam to electricity is also well established. However, as society focuses its concern on the environment and air and water quality, it has been recognized that the combustion of conventional biomass, even if plainly dried and burned, releases chemical components such as volatile organic compounds (VOC's) and particulate matter generated during the combustion process that tends to foul the air and fill it with smoke, dust and ash.
Conventional biomass fiber fueled plants have become very costly and time consuming to build because they must be engineered and designed to consume biomass of a certain nature and to mitigate particulate and volatile organic compound emissions resulting from the burning of biomass. Furthermore, these plants must operate on a 24 hour basis daily, year in and year out in order to be cost effective producers of green clean energy and clean heat. They cannot simply start and stop at will, and are therefore used to produce electrical energy known as ‘base-load’ or ‘firm base’ energy. They produce energy that costs the same whether it is produced at 3:00 AM or at 2:00 PM. However, it is well known that nighttime energy is less valuable than peak daytime energy.
Accordingly, the economics of biomass power plants are problematic because they do not fit all situations of affordable biomass consumption or timely electrical demand. Furthermore, these types of plants are fixed in location and not mobile and because of the heavy nature of their construction are set into concrete and steel, hard wired and plumbed into power grid transformer stations, permitted in one area to operate, permitted for one type of fuel and one type of ash output. They are also typically constructed proximate to a biomass fuel supply for which they are engineered, and which is generally located not more than an eighty to one hundred mile radius from the plant. In some circumstances, the biomass fuel supply is not even available year round, but is seasonally harvested, grown or aggregated.
One problem that has not yet been overcome simply by air drying or evaporative heating of the biomass until the biomass has a moisture content considered dry enough to combust, for example, under five (5) percent but generally less than 25%, is that all unprocessed and not specifically heat-treated biomass is hydroscopic and hydrophilic. Dry biomass will not stay at the same moisture content if exposed to humidity or weather. If it is dry, it will absorb moisture and become wet once again. Whether or not the moisture is cellular moisture or surface moisture, the water has a negative effect on the heat output of combusting biomass, as water is an extinguishing media that prevents or materially slows biomass combustion. Consequently, all unprocessed air dried or evaporative dried biomass that is non-specifically heat-treated will absorb ambient moisture.
Moreover, biomass dispersed into moisture laden fluids will absorb fluid and may prevent the biomass from being a suitable heat or energy generating fuel. Even when the biomass is air or evaporative dried mechanically or otherwise, lignin and cellulose fiber bound together in the dry biomass are hydrophilic and that allows the biomass to wick up and hold moisture thereby negatively impacting the combustion capability of the fuel product. In such cases, the biomass may require some form of pre-heating or re-drying immediately prior to or along with combustion.
Furthermore, and most significantly, the mechanically and chemically bound lignin and cellulose in biomass are not easily broken down sufficiently even through air drying and evaporative mechanical drying to allow the biomass to be cost effectively and commercially reduced in size and consistent character, such as, for example, into a finely ground powder or even into minute micro or nano particulate sizes amenable to forming a slurry, suspension or liquid solution or a colloidal dispersion. Without changing the chemical and mechanical nature of the biomass through a specifically designed heat-treating processes, the biomass within the slurry, suspension, liquid solution or colloidal dispersion will remain hydrophilic and will retain the original inherent chemical and vegetative compounds that contribute to VOC and particulate emission pollution when the biomass is combusted.
Recently, various technologies for heat-treating and processing biomass have been developed which serve to alter the character of the biomass in a manner so as to provide a processed specially heat-treated biomass derived material for fuels that is hydrophobic and resists moisture wick up and absorption. These technologies remove VOC's and cellular particulate matter from the biomass, such as, for example, hemicellulose, that produces smoke and harmful emissions on combustion, and impart a hydrophobic, friable condition to the remaining heat-treated biomass which can be more easily and cost effectively processed into smaller particles that are fine enough to form a colloidal dispersion when mixed with a fluid type carrier.
Use of these technologies reduces the weight of the biomass feedstock product, increases the entrained energy density per pound of the remaining product, and creates a homogenous dry solid that can be pressed into a pelletized or cubed product which can be transported over long distances to plant locations where the processed solid biomass fuels can be consumed more cost effectively than unprocessed pelletized or chipped biomass. These process treatments also result in a product that is able to burn transparently with coal in un-modified coal fired power plants or in conventional biomass power plants. The mix of biomass feedstock used to produce the end-processed product is not identifiable in the final heat treated product because it becomes homogeneous, both in appearance and energy content.
One method involving specialty heat treating of biomass is known as torrefaction. There are several known methods of torrefaction characterized by the method and type of equipment and handling of the biomass furnished product. Torrefaction is characterized by roasting a raw biomass for a certain time and using a particular temperature curve in the absence of oxygen so as to prevent combustion of the biomass, to create a fuel product that has certain desirable characteristics which exceed those found in ordinary biomass.
Supertorrefaction, or fast flash torrefaction, is a technology that, as its name implies, results in achieving an intermediate or end product much more rapidly than other methods. To effectively produce an acceptable end product, supertorrefaction requires the biomass feedstock to be pre-processed to reduce moisture in the feedstock and to ensure that the feedstock particles are appropriately sized before heat processing. The pre-processed biomass is then heated with heat transfer agents such as organic molten salts during the supertorrefaction process.
Torrefaction involves a thermochemical treatment of previously air dried or moisture evaporated biomass at temperatures generally in the range of 250 to 350° C. for a specified time. The time and temperature may be varied depending on the type of biomass, its particle size, consistency of mix of furnish, type of chemical and mechanical bonds of the cellulose and lignin present. The biomass, which is typically woody based and generally having a pre-processing moisture content of less than 15-25%, is specifically heat-treated, roasted and charred in the absence of oxygen until it breaks the lignocellulosic bonds, removes the VOC's and hemicellulose, burns off or gasifies some minerals, chemicals and ultimately chars and embrittles the mix of lignin and carbon fiber.
Using the torrefication process, a desirable furnish product can be created in a cost effective and appropriately commercial operating manner. Not all torrefaction technologies are suitable and not all automatically result in a desirable output product. When the processing is properly done, water contained in the biomass, as well as superfluous volatiles, primarily alcohols and hemicellulose, are released at lower temperatures and the biopolymers in the biomass, such as, for example, higher temperature burning oils, cellulose, and lignin remain. The process essentially fractures chemical and mechanical bonds, partly decomposing the biomass, and gives off various types of volatiles, low alcohols, some simple ash components and reducing or removing minerals salts from the resulting treated product.
The final torrefied biochar output product is a charred solid (not charcoal), relatively dry (average 2-5% moisture content or less), and blackened into a bio-char material that retains carbon, some lower oils, some traces of minerals, some gases, and some ash. The final product is hydrophobic and brittle, rendering it easily friable and suitable for pulverizing into a fine powder, and retains an energy content that is typically in the range of 9,500 BTUs per pound and 10,500 BTUs per pound. Under some time and temperatures, the energy density can exceed 12,000 BTUs per pound.
Since the torrefied biochar product is hydrophobic, it repels water and can be stored outdoors in most every outside climate condition including moist air or rain without any appreciable wick up change in moisture content or reduction of heating value, unlike the raw biomass from which it is made.
Moreover, given the torrefied biochar may be easily and cost effectively reduced to a finely ground and pulverized powder in micron, submicron and nano sized particles. Normally, this biochar would be pelletized or cubed for handling, storage and for eventual transport. As a cubed or pelletized product it can be compressed and densified to a higher density than raw biomass pellets or chips, and transported over greater distances at a lower cost than conventional biomass fuels and it can be combusted in any conventional biomass power plant, or for heat or for energy in any unmodified coal fired power plants. Leaving torrefied biochar in an unpelletized or uncubed state may allow undesirable dust to float in the air, which may create a hazardous storage condition, as an unwanted accumulation of torrefied dust particles in a confined storage space may result in a combustible or explosive air mixture.
The char process may be altered to accommodate biomass types having a moisture content of, for example, 30-45% or greater. For example, while heat-treatment torrefication of much drier biomass fiber is done at essentially low pressure or atmospheric pressure, a similar process resulting in.similar if not an identical finished biochar end product may be obtained using a process known as hydrothermal carbonization, or HTC.
The HTC process also heats the biomass but in the absence of oxygen and at a lower temperature and often with a longer exposure to heat, but at pressures of up to 700 psi or greater in an autoclave type environment. The resulting end product splits the raw biomass into a water laden liquid phase and a cellulosic lignin and carbon laden phase. This process also separates certain salts and other minerals and chemicals that can be diverted in the liquid phase from the cellulosic carbon minerals in the solid phase, and removes the moisture from the solid phase in the same process.
The HTC process has its own particular benefits for production operations. Biomass products processed in this manner generally include and begin with more wet (moisture laden) biomass fibers such as grasses and agricultural by-products, straws, wet agribusiness by-products and the like. The end product of the solid phase is also a friable, hydrophobic cellulose and lignin product that has the same ultimate grinding ability, hydrophobicity, and workability as the above described torrefied product and can be used much as the torrefied product described above.
A newer type of conversion process, known as CELF, or Co-Solvent Enhanced Lignocellulosic Fractionization, may also be used to process biomass types that, for example, consist primarily of smaller particles of woody based biomass, including such biomass as sawdust or shavings or agribusiness by-products such as hulls and seeds, shells, food or feed, processed waste such as cotton gin trash, grape pomace, crushed pits, feed mash or already ground smaller biomass fibers. This process is particularly useful where the output of the components from the biomass feedstock result in solutions which can be further processed and used for different purposes in different fuels, such as, for example, extracting alcohols and lighter oils, gasses, or solutions to be processed into gasoline or kerosene, or separation from heavier fuels such as biodiesel and ship's bunker fuels.
The CELF method processes the raw biomass furnish under lower heat and pressure than the previous processes resulting in a liquid component, which may include the solvents used to fractionate the components, water and a dissolved lignin component which can then be separated, and a solid cellulose component, which may be particulate in form, that can be extracted and used individually or together as building blocks for other fuels. Lignin and cellulose may then be processed into biofuel and cellulosic particles that will then be used or further processed to create submicron and nano particles by the same means of pulverizing and deriving powders as used with HTC or torrefication but, because of the chemical fractionization rate, it may be accomplished at a more rapid rate and at a lower temperature and shorter time to create a more diversely tailored output product.
A fourth process that may be used to create micron, submicron and minute nano-particles of biochar by specialized heat treatment is to use an abbreviated pyrolysis process where the biomass is processed in a much higher temperature environment, often at temperatures in excess of 500 degrees Centigrade, albeit for a shorter period of time, than in the previous processes and whereby the inherent VOC's and hemicellulose are removed rapidly in the beginning of the process and the resultant remaining cellulose and lignin product is charred but not completely pyrolized. In this form of heat treatment process, however, the off-gassed water vapor is removed and certain pyrolysis type oils, lower heavy oil, and tar compounds which are usually the last to be consumed and are turned to a gas vapor and distilled in a conventional pyrolysis process, instead remain in the residual lignin and cellulose biochar and are not removed from the cellular content of the carbon laden biochar.
The residual heavy oil and tar compounds that remain in the biochar particles after the abbreviated pyrolysis process increase the energy content of the char particles. This type of abbreviated pyrolysis process may be considered an advantageous method because the residual biochar itself has much of the energy that would otherwise have been already cooked out of it by the ordinary pyrolysis process and distilled into another product. In any event, the remaining biochar product, including the pyrolysis oil and tars, must be further processed to produce both a final biochar having hydrophobic and friable qualities.
All of the above processes provide a relatively dry (generally under 5% and more normally a 3% moisture content or less), particulate fuel that can be burned or gasified under the right conditions and in the right equipment to provide green, non-polluting heat and energy with a carbon neutral footprint and a substantially reduced emission curve as compared to conventional biomass or non-renewable fuels. However, the biochar product of the heat treatment processes described above is, without further processing and cautious handling, difficult to commercially bulk transport and store, dangerous to stockpile or deliver as a powder without causing a risk of airborne dust concentrations becoming an easily ignitable or even explosive mist, and difficult if not impossible to control and feed in a measured and controlled way into a variety of commonly used heat and energy generating equipment. It is also incompatible in dust form with ordinary bulk non-processed biomass fuels used in dedicated biomass heat or energy generation equipment.
Moreover, one approach to controlling the dust and storage problems of the torrefied product in a cost effective manner has been to pelletize or cube the torrefied biochar. However, pelletizing and cubing the biochar limits its use to equipment and feed streams that are designed only for such dry feedstock handling use.
Conventional liquid fuels today made from biomass are distilled, chemically cracked, fractionated, and refined through a number of highly complicated, expensive and critically engineered processes that destroy or remove the solid component from the fuel, extract sugars and/or other compounds, and in the end create a bio-oil or bio-gasoline or alcohol based fuel. No matter how these liquid biomass derived fuels are made, they are not solutions, liquid dispersions, or colloids because they have no particulate content in the final product. The process of creating a bio-gas, bio-oil, ethanol or methanol from raw biomass results in a by-product waste, sludge, or agglomerated lignin and cellulosic sugar depleted fiber and ash product. These waste by-products generally have been accorded little residual value, because their subsequent use relies on further processing the waste by-product to de-wet and dry the waste product before it can be burned or used as a soil amendment or component of animal feed without fostering undesirable bacteria or chemical compounds. Consequently, the conversion of these waste by-products has been complicated, problematic, and generally not cost effective.
What has been needed, and heretofore unavailable, is a practical, commercially viable and functional, low-cost process for producing and using a biochar based feedstock as a fuel to be used in a variety of commonly diverse heating and energy generation capacities, without requiring specifically dedicated, special purposed and designed and engineered biomass heating and electrical generating equipment. Such a biochar based feedstock should be able to be manufactured from a variety of different biomass furnishes, including various plant matter, including trees, bushes, agribusiness by-products, crops and grasses and other sources of raw biomass, for example, the waste product or sludge created by liquid biofuel manufacture. Such a biochar may be used in a number of diverse applications to create a fuel that can be used for the production of heat or energy. In some cases the biochar may be incorporated into a non-aqueous fluid that can be burned to produce heat or energy. The biochar may also be processed in such a manner that the liquid component of the raw biomass is separated and further processed to remove valuable minerals contained in the liquid component. Biochar based fuels should be able to be mixed with existing petroleum based fuels or refined biomass sourced oil based liquid fuels resulting in overall lower cost, lower emission fuels while maintaining or improving the energy content of the resultant fuel. The present invention satisfies these, and other needs.